Centering device



Filed June 5, 1951 INVENTOR. WILLIAM D. HIBBARD ATTORNEY United States Patent CENTERING DEVICE William D. Hibbard, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application June 5, 1951, Serial No. 230,056

Claims. (Cl. 74470) This invention relates to a mechanism adapted to return two relatively pivoted parts to a predetermined angular relationship When a force that has moved them out of this relationship is removed.

An object of the invention is to provide a mechanical linkage that will return an angularly displaced member to a predetermined position when released from positions on either side of a predetermined position.

Another object is to provide a centering device having adjusting means serving the purpose of determining accurately the centered position and of eliminating lost motion at the centered position.

Another object is to provide a mechanical linkage for centering a manually operated potentiometer.

Other objects will be evident from the following specification and claims, and from the drawing in which Figure 1 shows the centering mechanism in centered position, and with the potentiometer and cover removed,

Figure 2 shows the same mechanism displaced from the centered position,

Figure 3 shows the device with the potentiometer mounted over the centering mechanism, and

Figure 4 is an elevation taken in section along the line 44 of Figure 3.

The illustrated embodiment of the invention shows a manually operable potentiometer designed for use in connection with an airplane pilots control stick which is used to modify the course of an airplane as dictated by an autopilot. This potentiometer is carried within a knob at the top of the stick and is operated by turning the knob while the supporting stick remains relatively stationary. The stick is also movable forward and aft to control the airplane about its pitch axis, and laterally to control it about its roll axis, but that mechanism forms no part of the present invention. Reference is made, however, to Kwasniewski application, Serial Number 230,054 filed June 5, 1951, now Patent No. 2,625,050, issued January 13, 1953, directed to another centering device useful for that purpose. The present device is adapted to control turning of the airplane.

A supporting plate is secured to a flanged bushing 11, as seen in Figure 4. The bushing 11 is secured to the top end of a tubular member 12 and is rotatably mounted with respect thereto. The lower end of the bushing engages a shoulder 13 on the tubular member 12 and the upper end of the bushing is confined by a snap ring 15 carried in a groove in the tubular member 12.

The tubular member 12 has an extension projecting upwardly from supporting plate 10 comprising a cam 17, and above that a rod 18, the rod being coaxial with the pivotal axis of the tubular member 12 in the bushing 11. The upper surface of the cam 17, as seen in Figures 1 and 2, is also coaxial with the axis of the tubular member 12, and is herein shown as being of the same radius as the rod 18. An insulating plate is supported in spaced relation to the plate 10 by a pair of 'ice posts 21 and 22. As seen in Figures 3 and 4, the plate 20 carries an electrical resistance winding 24 in fixed relation with respect to the plate 10. An insulating plate 26 is secured to the top end of the shaft 18 for rotation therewith. An electrical contact arm 27 is secured to the plate 26 and carries an electrical contact 29 adapted to engage the resistance winding 24. The resistance winding 24 together with the contact arm 27 and contact 29 comprise a potentiometer adapted to be positioned by relative movement between the supporting plate 10 and the member 12. A cover 31, suitably secured to the plate 10, encloses the mechanism above the plate 10 and is made in the shape of a knob to facilitate manual positioning of the potentiometer.

As seen in Figures 1 and 2, a pair of levers 33 and 34 are pivotally mounted on the plate 10 on a pair of pins 35 and 36 which have their axes parallel to the pivotal axis of the member 12 in the supporting plate 10. The levers 33 and 34 are so pivoted as to be movable toward and away from the pivotal axis of the member 12. A rod 40 extends through openings in the lower ends of both levers, as seen in Figures 1 and 2, and carries a snap ring at each end which serve as abutments for a pair of compression springs 43 and 44, the opposite ends of which engage the outer surfaces of the levers 33 and 34. The springs 43 and 44 bias the levers 33 and 34 toward the pivotal axis of the member 12 in the plate 10.

A fiat plate 46 made of resilient sheet metal is carried on the inner surface of the lever 33 and is provided with a projection 47 of reduced size that extends through a hole in the lever to hold it in place. The upper edge of the plate 46 as seen in Figures 1 and 2 engages a notch in the lever 33, the notch serving as a pivotal support for the portion of the plate 46 that extends generally parallel to the length of the lever. The reduced extension 47 of the plate 46 is shaped to bias the plate 46 toward the lever. An adjusting screw 48 is screw threaded in the lever 33 and abuts the underside of the plate 46 to adjust the angular relationship between the plate 46 and the lever 33. A similar plate 50 is carried by the lever 34 and has a reduced extension 51 extending through the lever and an adjusting screw 52 for determining its angular relation with respect to the lever 34. It will be seen that both the plates 46 and 50 present plain surfaces for engagement with the cam 17. The cam 17, likewise, presents a pair of plain surfaces for engagement with the plates 46 and 50. The plain surfaces of the cam 17 joins smoothly into the cylindrical surface thereof and in the center position as seen in Figure l, the opposing plates 46 and 50 engage elements of the cylindrical surface end of the opposing plain surfaces as well.

In Figure 2 the supporting plate 10 has been rotated counterclockwise with respect to the member 12 so that the cam 17 now engages the plate 46 only at an extremity of its left-hand plain surface, while the plate 50 engages the cam only on an element of the cylindrical surface thereof. The lever 33 has been rotated in a clockwise direction with respect to the plate 10 and energy has been stored in the springs 43 and 44 which is available to restore the mechanism to its center position upon release of the knob 31. Turning the knob in the opposite direction will, of course, result in displacement of the lever 34. In order to limit the possible angular displacement of the potentiometer, the post 21 is provided with an adjustable stop screw 55 adapted to engage the outer surface of the lever 33 and the post 22 carries an adjustable stop screw 56 adapted to engage the outer surface of the lever 34.

Since the system with which the potentiometer is to be associated may require that the centered position of the potentiometer slider does not exactly correspond to its physical center, and since manufacturing tolerances of the-parts must beprovided for, it is necessary to provide adjustment both forthe location of the centered position and to assure a definite centered position. In Order to provide a definite centered position, it is necessary-toadjust' the screws 48 and-52 so that the plates 46 and' 50 engage the cam 17 at spaced points along the cam extending laterally from the axis thereof. If the plates 46 and 50 are too close together at either the top or the bottom as seen in Figures 1 and 2 a certain amount of relative movement between the supporting plate 10 and the member12 would be permitted without changing the length of the springs 43 and 44. In order to adjust the centered position of the potentiometer the adjusting screws 48 and'S'Z are relatively adjusted to provide the desired angular relation between the supporting plate 10 and member 12.

In order to provide smooth operation and long life, cam 17, and plates 46 and 50 are provided with extended surfaces. Certain phases of the invention, however, contemplate the plates 46 and 50 merely as arms pivotally adjustable with respect to the levers 33 and 34. Obviously, the invention will have many uses other than in the airplane control stick described.

I claim as my invention:

1. Centering means for an oscillatable member comprising, a support, a member pivoted in said support, first and second levers pivotally mounted on said support for movement toward and away from the pivotal axis of said member, a first arm pivoted on said first lever on an axis parallel to the pivotal axis of said first lever, a second arm pivoted on said second lever on an axis parallel to the pivotal axis of said second lever, spring means biasing both levers toward the pivotal axis of said member, said member having a portion lying between said arms and shaped to engage each of said arms at two points spaced diiierent distances from the pivotal axis of the associated lever, and means for varying the angular relation between each arm and associated lever.

2. Centering means for an oscillatable member comprising, asupport, a member pivoted in said support, first and second levers pivotally mounted on said support for movement toward and away from the pivotal axis of said member, a first arm pivoted on said first lever on an axis parallel to the pivotal axis of said first lever, a second arm pivoted on said second lever on an axis parallel to the pivotal axis of said second lever, spring means biasing both levers toward the pivotal axis of said member, said member having an arcuate surface that is coaxial with the'pivotal axis thereof and adapted to engage both of said arms, and said member further having a pair of oppositely disposed surfaces adapted to engage portions of said arms spaced with respect to the pivotal axes of said levers from the portions thereof engaged by said arcuate surface, and means for varying the angular relation between each arm. and associated lever.

3. Centering meansfor an oscillatable member comprising, a support, a member pivoted in said support, first and second levers pivotally mounted on said support for movement toward and away from the pivotal axis of said member, a first arm pivoted on said first lever on an axis parallel to the pivotal axis of said first leverga second arm pivoted on said second lever on an axis parallel to the pivotal axis of said second lever, spring means biasing both levers toward the pivotal axis of said member, said member having a portion lying between said arms, said portionhaving opposing flat surfaces adapted to engage flat surfaces on said arms, and means for varying the angular relation between each arm and associated lever.

4. Centering means for an oscillatable member comprising, a support, a member pivoted in said support, first and second levers pivotally mounted on said support for movement toward and away from the pivotal axis of said member, a first arm pivoted on said first lever on an axis parallel to the pivotal axis of said first lever, a second arm pivoted on said second lever on an axis parallel to the pivotal axis of said second lever, spring means biasing both levers toward the pivotal axis of said member, resilient means biasing each arm in one angular direction with respect to its associated lever, said member having a portion lying'between said arms and shaped to engage each of said arms at two points spaced different port and said member, said control means having a nullintermediate position, first and second levers pivotally mounted on said support for movement toward and'away from the pivotal-axis of said member, a first arm pivoted on said first lever on an axis parallel to the pivotal axis of saidfirstlever, a second armpivoted on said second lever on an axis parallel to the pivotal axis of said second lever, spring means biasing both levers toward the pivotal axis of said member, said member having a portion lying between said arms and shapedto engage each of said arms at two points spaced different distances from the pivotal axis of the associated lever and'means for varying the angular relation between each arm and associated lever so that said member engages each of said arms at said two spaced points when said control means is in its null position.

References-Cited in the file of this patent UNITED STATES PATENTS 713,490 Pottin Nov. 11, 1902 1,768,625 Olsen -a July 1,1930 2,066,287 Chandler Dec. 29, 1936 2,220,180 Spitzglass et al. Nov. 5, 1940 2,427,621 Peterson Sept. 16, 1947 2,531,764 Binns et a1. Nov. 28, 1950 FOREIGN PATENTS 687,518 Germany Jan. 31, 1940 

